1. Field of the Invention
The present invention relates to water dilutable, polyester polyols which contain urethane and carbonate groups; water dilutable binders based on these polyester polyols; and the use of the polyester polyols as a binder component in aqueous coating and jointing compositions.
2. Description of the Prior Art
In many applications modern aqueous binders are replacing solvent-based binders. This applies in particular to those areas in which aqueous binders have specific advantages, such as in electrophoretic enamelling.
For applications with high property requirements, such as clear automobile lacquers, aqueous binders which satisfy these demands have not previously been available. In EP-A 0,455,028, for example, emulsion copolymers are described which produce automobile clear lacquers in combination with melamine resins. These resins already possess reasonable properties, but are deficient with regard to optical properties, such as sheen, and flowability.
In addition to very good optical properties, automobile clear lacquers must also possess excellent resistance to chemicals and solvents or petrol. In this respect, it should be ensured that the coatings retain their properties for as long as possible even when there is progressive pollution of the environment. In addition, aqueous binders should contain as little organic solvent as possible in order to satisfy strict standards with reference to environmental acceptability.
It is an object of the present invention to provide aqueous binders which are suitable for applications with high property requirements, such as clear automobile coatings, which require in very good optical properties and excellent resistance to chemicals and solvents, which can also be prepared economically and which contain little volatile organic solvent.
These objects may be achieved with the water dilutable, polyester polyols according to the invention which contain urethane and carbonate segments and which are described in more detail hereinafter. The polyester polyols according to the invention are extremely compatible with water and also with other known lacquer components, contain few volatile organic substances and may be processed in combination with the known cross-linking resins to give high-quality, storage-stable, aqueous coating and jointing compositions.